A typical pressure detection device in an injection molding machine includes a fixed mold supported by a fixed platen of a mold clamping device, a movable mold supported by a movable platen of the mold clamping device, and a pressure sensor configured to detect an inner pressure of a cavity defined by the fixed mold and the movable mold, the pressure sensor being attached to a rear end surface of an ejector pin of a movable mold (for example, see Patent Literature 1).
Such a pressure detection device in the injection molding machine is configured to store, as a correction value, a pressure detection value based on an output from the pressure sensor during a predetermined period from completion of ejection using an ejector pin to a mold-opened state where an inner pressure in the mold reaches zero in principle, and correct an output from the pressure sensor at the time of pressure detection with the correction value.